JPH09163185A - S/n improving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the discontinuous distortion of signals resulting from DC- shifting of an input signal to improve the S/N. SOLUTION: A comparison and difference calculation means 15 obtains a direction in DC shift and a level difference between an input signal and a reference signal, a shift amount control means 16 obtains the DC shift depending on a noise amount, a level difference and the level of the input signal, and a DC shift means 17 conducts DC shift processing in response to the DC shift direction and the DC shift amount with respect to the input signal. Thus, discontinuous distortion of signals after DC shift is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SN ratio improving device, and more particularly, it uses a DC shift type noise reducer for realizing noise reduction by level shifting (DC shifting) the value of an input signal on which noise is superimposed. The present invention relates to an SN ratio improving device.

[0002]

2. Description of the Related Art A noise reducer (hereinafter referred to as NR) for improving the SN ratio of an input signal (video signal) is
For example, "Proposal of DC addition type noise reducer and MUSE
Development of noise reducer for decoder video processing "(Izumi et al. 4, The Television Society Journal, Vol. 48, No. 12,
pp1553 to 1564 (1994)), there is an NR proposed for a high definition receiver of MUSE (muse) system (hereinafter referred to as MUSE decoder). This NR is also called a DC shift type NR,
The outline is described below.

FIG. 4 shows a block diagram of an electric circuit of an SN ratio improving apparatus using a DC shift type NR. Reference numeral 41 is an input terminal for inputting a MUSE signal, and 42 is an input terminal for a control signal indicating reception C / N of the input MUSE signal. Reference numeral 44 is a decoding means for returning the transmitted MUSE signal to the original wideband high-definition video input signal. Hereinafter, the high-definition video input signal decoded and restored by the decoding means 44 will be referred to as an original input signal. Reference numeral 46 is a reference signal generating means for predicting an original ideal high-definition signal in which noise is not superimposed on the original input signal to generate a reference signal, and a median filter is used. Reference numeral 45 is a delay means for delaying the original input signal by a time corresponding to a delay time until the reference signal generating means 46 generates a reference signal based on the original input signal. 47
Is a level comparison means for comparing the signal levels of the original input signal delayed by the delay means 45 and the reference signal. Reference numeral 48 denotes a DC shift means for level-shifting the delayed original input signal. The DC level shift direction is determined according to the comparison result of the level comparison means 47, and the received C signal is received.
A DC shift amount is determined according to / N, and the DC shift amount is added to the delayed original input signal. An output terminal 43 outputs the signal processed by this circuit.

The principle of this DC shift type NR will be described.
To reduce the noise superimposed on the original input signal obtained by decoding the MUSE input signal, the noise component is subtracted or added from the original input signal, that is, the level of the original input signal is DC-shifted by the noise amount. It is possible to obtain the original signal (video signal) on which noise is not superimposed. The DC shift type NR is equivalent to that the original input signal is DC-shifted by the amount of noise superimposed on the original input signal to bring the original input signal close to the reference video signal on which noise is not superimposed. The noise is compressed to improve the SN ratio.

The reference signal generating means 46 predicts an original high-definition video signal on which noise is not superimposed and generates a reference signal. The level comparing means 47 is
The level of this reference signal is compared with the level of the original input signal to output a control signal indicating the shift direction. For example, "1" is output when the original input signal is large, and "0" is output when the original input signal is small. Then, the DC shift means 48 refers to the shift direction indicated by the control signal, and when the original input signal is larger than the reference signal, a DC component (DC shift amount) corresponding to the received C / N from the original input signal.
To approach the reference signal by subjecting the original input signal to a DC shift process in the direction of decreasing, and in the direction of adding a direct current component (DC shift amount) to the original input signal when the original input signal is smaller than the reference signal. The original input signal is DC
The shift processing brings the signal closer to the reference signal, compresses the noise component, and performs signal processing for obtaining the original video signal.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The shift type NR realizes the improvement of the SN ratio of the original input signal by the DC shift of the original input signal, and this DC shift amount is controlled by the noise amount included in the original input signal. Since this noise amount is originally obtained by integrating the change amount of the signal in a fixed period in which there is no signal change, this noise (detection) amount becomes a signal having a long cycle every fixed period. Therefore, this noise detection amount can be considered to be a fixed value compared to the changing original input signal, and, for example, a certain amount of DC shift is performed on the original input signal of the entire screen. Therefore, when the original input signal is DC-shifted and brought close to the reference signal, the DC shift amount is constant regardless of the level difference between the two signals. Therefore, near the intersection of these two signals, D
There is a problem that discontinuous distortion occurs in the output signal after the C shift.

This discontinuous distortion will be described with reference to FIG. Here, 51 is an original input signal, 52 is a reference signal, 53 is a DC-shifted output signal, and dV is DC.
It represents the shift amount.

The original input signal 51 is compared with the reference signal 52, and if the former is larger, the arithmetic processing of (original input signal −dV) is performed, and if the latter is larger, (original input signal + dV).
Then, the original input signal 51 is DC-shifted so as to be closer to the reference signal 52. At this time, DC
Focusing on the intersection of the shifted original input signal 51 and the reference signal 52, the original input signal 51 is DC-shifted in the opposite direction before and after this intersection. Output signal 53 becomes a discontinuous signal. Further, in a region where the level difference between the original input signal 51 and the reference signal 52 is small, the DC shift amount for the original input signal 51 becomes larger than the level difference. Therefore, the signal after the DC shift processing becomes a rectangular wave signal, and the information originally possessed by the original input signal 51 is lost by performing this DC shift processing, and, for example, noise such as block distortion is generated. It will be.

An object of the present invention is to solve such a problem and reduce the discontinuous portion generated in the output signal by performing the DC shift processing, so that the original video signal can be accurately reproduced. It is to realize an SN ratio improving device.

[0010]

According to the present invention, an input signal containing a video signal and noise is compared with a reference signal corresponding to an input signal containing no noise predicted from the input signal, and a DC shift direction of the input signal is compared. And an SN ratio improving device for improving the SN ratio of the input signal by DC-shifting the input signal in the DC shift direction in accordance with a control signal indicating the amount of noise included in the input signal, The DC shift amount of the input signal is changed according to the signal level of the input signal and the level difference between the input signal and the reference signal.

The control of the DC shift amount based on the level difference is stopped when the amount of noise included in the input signal is equal to or less than a predetermined set value.

By changing the DC shift amount according to the signal level of the input signal and the level difference between the input signal and the reference signal, it is possible to perform the DC shift amount control in which the discontinuity of the signal after the DC shift process is suppressed. . Further, when the noise amount is small, the shift amount control characteristic is switched to obtain a high SN ratio improving effect.

[0013]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an SN ratio improving apparatus according to the present invention using a DC shift type NR. Reference numeral 11 is an input terminal into which an input signal including a video signal in the system comes in, 12 is an input terminal for data indicating the amount of noise included in the input signal, and 14 is a reference signal by predicting a video signal containing no noise. The reference signal generating means for outputting, 15 compares the levels of the input signal and the reference signal with each other, and comparison / difference calculating means for detecting the level difference between these two signals, and 16 the noise introduced from the input terminal 12. D determined by a logical operation of the noise amount, the level difference between the input signal and the reference signal, and the level of the input signal according to the level of the amount (signal).
A shift amount control means for selectively outputting either the C shift amount or the DC shift amount determined by the logical operation of the noise amount and the level of the input signal, and 17 is a DC shift for performing the DC shift of the input signal. Means, 18 is a delay means for delaying the input signal by a time corresponding to a delay time until the reference signal generating means generates a reference signal based on the input signal, and 13 is an output signal after performing a DC shift process. Is an output terminal for outputting.

The reference signal generating means 14 uses a median filter as in the conventional device shown in FIG. The median filter includes a horizontal (and / or vertical) delay element, and serves as an LPF for obtaining an intermediate value of a target pixel area. Specifically, the reference signal generating means 14 includes, for a certain target pixel, the pixel and the pixel which is adjacent to the target pixel in the horizontal direction (and / or the vertical direction) and further spatially. An intermediate value or the most existing value among the pixels in the area is obtained as the original ideal predicted value of the input signal with no noise superimposed, and this is output as the reference signal for the input signal. Comparison
The difference calculation means 15 compares the reference signal output from the reference signal generation means 14 with the input signal delayed by the delay means 18, compares the levels of these two signals, and the DC shift means 17 performs comparison. It is output as a control signal in the DC shift direction. Further, the comparison / difference calculation means 15 obtains the difference between the delayed input signal and the reference signal and outputs it as one of the shift amount control signals. The control signal in the DC shift direction, the level difference signal, the delayed input signal, and the noise amount signal introduced from the input terminal 12 are input to the shift amount control means 16 as control signals for determining the DC shift amount. To be done.

The shift amount control means 16 performs a logical operation on the level difference between the input signal and the reference signal, the noise amount signal introduced from the input terminal 12 and the delayed signal level of the input signal itself to perform a DC shift amount control signal. Is generated, and this is given to the DC shift means 17. However, when the amount of noise introduced from the input terminal 12 is small, that is, when the SN ratio is good, the reflection of the level difference signal is stopped in order to avoid a decrease in the SN ratio improving effect. In this way,
An appropriate DC shift amount is set using the noise amount, the level difference, and the signal level of the input signal itself.

FIG. 2 is a block diagram of the shift amount control means 16 for performing such shift amount control processing. 12 is an input terminal for inputting a noise amount signal, 22 is an input terminal for inputting a level difference signal, 23 is an input terminal for inputting a delayed input signal (video signal), 25 is a noise amount coefficient unit, 26
Is a noise amount discriminating means, 27 is a level difference coefficient unit, 28 is an input signal level coefficient unit, 29 is a level difference signal selecting unit, 3
Reference numeral 0 is a shift amount determining means, and 24 is an output terminal for outputting a shift amount signal.

The noise amount coefficient unit 25 performs non-linear weighting on the noise amount signal input from the input terminal 12 and supplies it to the shift amount determining means 30. The noise amount determination means 26 determines whether or not the amount of noise input from the input terminal 12 is less than or equal to a set value, and a selection control signal for controlling the level difference signal selection means 29 and the shift amount determination means 3.
ON / OFF to control the DC shift amount at 0
Output as an OFF control signal. Level difference coefficient device 27
Receives the level difference signal input from the input terminal 22, non-linearly weights the level difference signal for finely controlling the shift amount when the level difference is small, and supplies the level difference signal selecting means 29. Input signal level coefficient unit 28
Is an input signal (video signal) input from the input terminal 23.
Are similarly weighted and output.

The level difference signal selecting means 29 selects and shifts the output signal of the level difference coefficient device 27 based on the control signal from the noise amount judging means 26, for example, when the noise amount is equal to or larger than a certain set value. The output signal of the level difference coefficient unit 27 is blocked so that the output signal of the level difference coefficient unit 27 is not supplied to the shift amount determination unit 30 when the noise amount is equal to or less than the set value. .

The shift amount determining means 30 logically operates each output signal of the noise amount coefficient unit 25, the input signal level coefficient unit 28, and the level difference coefficient unit 27 selected by the level difference signal selecting unit 29 to perform a DC shift amount. To decide.

As described above, the shift amount determining means 30 weights the weighted noise amount signal from the noise amount coefficient device 25 and the weighting from the level difference signal selecting means 29 when the noise amount is equal to or larger than a set value. The level difference signal and the weighted input signal from the input signal level coefficient unit 28 are input to determine the DC shift amount, and when the noise amount is less than or equal to a certain set value, the weighted noise amount signal from the noise amount coefficient unit 25. And the weighted input signal from the input signal level coefficient unit 28 is input to determine the DC shift amount. Therefore, in a region where the amount of noise is large, it is possible to perform a highly accurate SN ratio improvement process that reduces the discontinuous portion of the distortion due to the DC shift process. Further, it is possible to perform a corresponding improvement in the SN ratio even in a region where the noise amount is small. Then, for example, when there is almost no noise amount, the DC shift amount is forcibly set to "0" by the control signal supplied from the noise amount determination means 26, thereby avoiding the distortion due to the DC shift process. You can

Such a shift amount control means 16 is shown in FIG.
It can be implemented by modifying it as shown in the block diagram of FIG. Reference numeral 71 is an input terminal for the noise amount determination signal output from the noise amount determination means 26 described above, 72 and 73 are minimum value selection means for selecting the minimum value of different input signals, and 74 is a switch means. The same reference numerals are given to the circuit means equivalent to and the description thereof will be omitted.

The feature of this modified example is that the shift amount determining means 30 enclosed by a broken line has two minimum value selecting means 72, 7.
3 and switch means 74. According to such a circuit configuration, for example, when there is no level difference from the input terminal 22, the minimum value selecting means 72 selects the level difference signal even if the amount of noise from the input terminal 12 is large. Excessive DC shift can be prevented.

FIG. 3 is a block diagram of the DC shift means 17 for shifting the level of the input signal based on the DC shift amount thus determined. Reference numeral 31 is an input terminal for inputting a control signal indicating the DC shift direction output from the comparison / difference calculating means 15, 32 is an input terminal for inputting a DC shift amount signal output from the shift amount controlling means 16, 3
3 is an input signal (video signal) output from the delay means 18
, 35 is a synthesizing means for synthesizing the control signal input from the input terminal 31 and the DC shift amount signal input from the input terminal 32, 36 is a DC shift addition means, and 13 is a DC shift process. It is the output terminal that outputs the latter signal.

The synthesizing means 35 synthesizes, for example, a control signal of 1-bit code data indicating the shift direction input from the input terminal 31 and a shift amount signal of n-bit absolute value data input from the input terminal 32. By doing
The sign bit is added to the MSB side of the absolute value data (n
+1) sign bit-added absolute value data (DC shift amount signal) is generated and input to the DC shift addition means 36. The DC shift addition means 36 adds the DC shift amount of the absolute value data with the sign bit from the synthesis means 35 to the input signal (video signal) to be input. For example, when the sign bit is "0", the DC shift amount is added to the input signal (video signal), and when the sign bit is "1", the DC shift amount is subtracted from the input signal (video signal), The DC shift is realized in consideration of the shift direction indicated by the control signal. That is, noise reduction is realized by bringing the input signal closer to the reference signal by the shift amount considering the noise amount, the level difference between the input signal and the reference signal, and the level of the input signal itself, and improves the SN ratio. be able to.

FIG. 6 shows the result of the DC shift processing in this embodiment. Reference numeral 61 is an incoming input signal (video signal), 62 is a reference signal, and 63 is a level-shifted signal. In the vicinity of the intersection of the input signal 61 and the reference signal 62, the shift amount of the input signal is controlled by the level shift, the noise amount, and the DC shift amount according to the level of the input signal. By comparison, discontinuous distortion of the signal after the DC shift process is reduced, and the signal is brought closer to the reference signal predicted as a video signal on which noise is not superimposed.

Further, so far, the DC considering the level difference is used.
Shift amount control and DC by level difference according to noise amount
Although one embodiment of the control for turning ON / OFF the shift control has been described with reference to FIGS. 1 to 3, the present invention is not limited to this. The shift amount control and the DC shift may be performed separately, or two shift amount control means and two level shift means may be used.

[0028]

INDUSTRIAL APPLICABILITY The present invention is an SN based on a DC shift type NR.
In the ratio improvement, the DC shift amount is controlled by the noise amount included in the input signal, the magnitude relationship between the input signal and the reference signal, and the level difference between the input signal and the reference signal. Therefore, there is an effect that it is possible to reduce discontinuous distortion of the signal after the shift processing that occurs near the intersection of the input signal and the reference signal. Further, in the shift amount control considering the level difference, when the noise amount is small, that is, when the SN ratio is good, the control based on the level difference is stopped. As a result, when the shift amount control considering the level difference is performed, it is possible to avoid a decrease in the SN ratio improving effect when the SN ratio is good. Therefore, the effect of improving the SN ratio improving effect is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an SN ratio improvement apparatus using a DC shift type NR according to the present invention.

FIG. 2 is a block diagram of shift amount control means in the SN ratio improving device according to the present invention.

FIG. 3 is a block diagram of a DC shift means in the SN ratio improving means according to the present invention.

FIG. 4 is a block diagram of a conventional SN ratio improving apparatus using a DC shift type NR.

FIG. 5 is a DC shift characteristic diagram in a conventional SN ratio improving device.

FIG. 6 is a DC shift characteristic diagram in the SN ratio improving apparatus according to the present invention.

FIG. 7 is a block diagram showing a modified example of the shift amount control means in the SN ratio improving device according to the present invention.

[Explanation of symbols]

11 ... Input signal (video signal) input terminal, 12 ... Noise amount signal input terminal, 13 ... DC shift processing signal output terminal, 14 ... Reference signal generating means, 15 ... Comparison / difference calculating means, 16 ... Shift amount Control means, 17 ... DC shift means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Sugiyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Multimedia system development headquarters (72) Mitsuo Nakajima Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa 292 Hitachi Ltd., Multimedia Systems Development Headquarters (72) Inventor Hatsuji Kimura Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture 292 Hitachi Systems Ltd. Multimedia Systems Development Headquarters (72) Inventor Keiichiro Shimada Gunma 111 Nishiyokote-cho, Takasaki-shi, Japan Within Hitachi, Ltd.Semiconductor Division (72) Inventor Yuichi Ninomiya 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory (72) Inventor Koichi Yamaguchi Tokyo 1-10-11 Kinuta, Setagaya-ku Japan Broadcasting Corporation Broadcasting Technology (72) Inventor Yoshinori Izumi 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory (72) Inventor Seiichi Koshi 2-2-1 Shinnan, Shibuya-ku, Tokyo Within the Association Broadcasting Center (72) Inventor Masahide Naemura 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Research Institute (72) Inventor Jun Fukuda 1-10-11 Kinuta, Setagaya-ku, Tokyo Broadcasting Association Broadcast Technology Institute

Claims (4)

[Claims] 1. A DC shift direction of an input signal is obtained by comparing an input signal containing a video signal and noise with a reference signal corresponding to an input signal containing no noise predicted from the input signal. In an SN ratio improving device configured to improve the SN ratio of the input signal by performing a DC shift in the DC shift direction in accordance with a control signal indicating the amount of noise included in the input signal, the DC shift amount of the input signal is changed. A signal-to-noise ratio improving apparatus characterized in that the signal level of the input signal and the level difference between the input signal and the reference signal are changed. 2. The SN ratio improving device according to claim 1, wherein when the amount of noise contained in the input signal is less than a predetermined set value, the control of the amount of DC shift due to the level difference is stopped. 3. A first input means for inputting a video signal containing noise as an input signal, a second input means for inputting a control signal indicating the amount of noise included in the input signal, and based on the input signal. Reference signal generating means for predicting an ideal signal containing no noise and generating it as a reference signal is compared with the signal level of the input signal and the reference signal to generate a control signal indicating the DC shift direction. In a signal-to-noise ratio improving device comprising a level comparing means and a DC shift means for DC-shifting the input signal in the DC shift direction according to the noise amount, a difference calculating means for obtaining a signal level difference between the input signal and a reference signal. And a DC shift amount control means for obtaining a DC shift amount according to the signal level of the input signal, the noise amount, and the signal level difference. S characterized by the provision of steps
N ratio improvement device. 4. The noise amount discriminating means for discriminating the noise amount, according to claim 3,
An SN ratio improving device comprising a level difference signal selecting means for stopping the DC shift amount control by the level difference signal when the noise amount is small based on the noise amount discrimination result.